Equivalence of magnetic field and particle dilution in the strange metal state of CeCoIn$_5$

Abstract

The Bardeen-Cooper-Schrieffer mechanism for superconductivity is a triumph of the theory of many-body systems. Implicit in its formulation is the existence of long-lived (quasi)particles, originating from the electronic building blocks of the materials, which interact to form Cooper pairs that move coherently in lock-step. The challenge of unconventional superconductors is that it is not only unclear what the nature of the interactions are, but whether the familiar quasi-particles that form a superconducting condensate even exist. In this work, we reveal, by the study of applied magnetic field in electronically diluted materials, that the metallic properties of the unconventional superconductor CeCoIn$_5$ are determined by the degree of quantum entanglement that (Kondo) hybridizes local and itinerant electrons. This work suggests that the properties of the strange metallic state are a reflection of the disentanglement of the many-body state into the underlying electronic building blocks of the system itself.